This invention relates to a process for heat treating food product. The process is advantageously used for pasteurizing and/or tenderizing proteinaceous food product.
Pasteurizing of proteinaceous food product can be carried out by heating to destroy infectious organisms such as salmonella. Pasteurization may be defined as heat treatment for the purpose of killing or inactivating disease-causing organisms. For example for milk, a minimum exposure for pasteurization is 62.degree. C. for 30 minutes or 72.degree. C. for 15 seconds. The latter exposure is called flash pasteurization. Complete sterilization may require ultra-high pasteurization such as treatment at 94.degree. C. for 3 seconds to 150.degree. C. for 1 second to kill pathogenic bacteria and inactivate enzymes that cause deterioration and to provide for satisfactory storage life.
Minimum food safety processing standards for various commodities have been promulgated and are enforced by the United States Department of Agriculture (USDA). Pasteurization may be defined in accord with the standards mandated by the USDA. The Nutrition Action Health Letter published by the Center For Science In The Public Interest (July/August 1991 Edition, Vol. 18, No. 6, "Name Your (Food) Poison") describes concern with the growing number of cases of food poisoning due to food infections.
Many known processes for pasteurizing food are insufficient to assure safety of some foods from infections or cannot be applied to some food products. The "Name Your (Food) Poison" article reports that dairy products, eggs, poultry, red meat and seafood, in that order are the most common causes of food poisoning. Shell eggs are particularly difficult to pasteurize because of their structure. The article indicates that one of 10,000 eggs is contaminated with salmonella enteritis.
U.S. Pat. No. 4,808,425 to Swartzel et al. teaches a method of "ultrapasteurizing" a liquid whole egg product". The liquid whole egg product is passed as a continuous stream through a pasteurizing apparatus. The liquid whole egg product is heated to a predetermined real temperature by contacting the product with a heated surface. The total thermal treatment received by the whole egg product is prescribed by an equivalent temperature and an equivalent time that are defined to pasteurize the material but insufficient to cause coagulation (loss of functionality) of product.
U.S. Pat. No. 5,290,583 to Reznik et al. relates to an electroheating process for treating liquid egg. The process comprises the steps of electroheating the liquid egg with an AC electric current having a frequency effective to heat the liquid egg without electrolysis at a rate to avoid detrimental coagulation (loss of functionality). The liquid egg is held at a temperature sufficient to achieve pasteurization.
Functionality or functional properties of eggs relate to the volume, structure, texture and keeping quality of baked products produced by the eggs. Functionality is defined herein as the capability of a proteinaceous food product to provide the properties of the product that has not been treated by the process of the present invention. Loss of functionality is determined by observing the loss of quality of the food product. For example, spoilage or cooking is a loss of functionality of meat in a process designed for aging of meat without cooking. Coagulation is a loss of functionality of shell eggs during pasteurization. Cooking and/or loss of taste or texture is a loss of functionality of oysters that are to be eaten uncooked.
The extent to which functional properties of a proteinaceous food product are affected by heating may be determined by testing the performance of the product under conditions in which the damage is readily observed. For example, functionality of eggs can be established by determining the quality of food products that depend upon the quality of coagulation of the egg. Such food products may include custards and pie fillings and loaves or croquettes which depend upon the binding of food together that may be provided by the quality of egg coagulation. The functional properties may also include the elasticity of an egg protein film or the emulsifying ability to disperse oil in the making of mayonnaise and salad dressings. Functionality or functional properties of other food product are similarly established in terms of the capability of the food product to perform intended purposes after heat treatment including retaining a "natural" taste and texture.
While heat treatment may be effective in pasteurizing proteinaceous food product, heating at the same time may destroy some functionality or functional properties of the product. The present invention provides a process for heat treating proteinaceous food product that achieves a delicate balancing of effective heat treatment without destruction of functionality or functional properties.
The heat treating process of the present invention also provides a method of quick aging of meat by exposure to an elevated temperature without decomposition of the food product by cooking. Aging a meat can be carried out by storing pieces of meat in a refrigerated space for a time sufficient to permit natural enzymes to complete a tenderizing process. Enzymes in the meat continue to function post-mortem to catalyze the hydrolysis of collagen and other proteins. The enzymes break down connective tissue so that the meat becomes tender and flavorful. After aging, the texture of the meat is more acceptable to the consuming public.
During aging, the meat is generally refrigerated at a temperature of about 34.degree. F. to suppress bacterial growth and at a relative humidity of about 80% to suppress mold growth. However at these conditions, the rate of enzymatic action is suppressed. An average of twenty-one days or more is often required to obtain satisfactory tenderizing. Substantial space in a refrigeration facility is required to store the meat for this period of time.
Increasing the temperature used in the aging process accelerates activity of the enzymes for tenderizing meat. However, bacterial activity is also increased. Slime growth, putrefaction and mold growth result in spoilage and can cause a substantial loss of usable meat. Maintaining low humidity in the refrigerated space to retard mold growth tends to desiccate and discolor meat. The desiccated and discolored parts must be trimmed. Additionally, low humidity causes shrinkage.
U.S. Pat. No. 2,713,002 to Williams proposes aging meat by storing a carcass in the presence of ultra-violet radiation. The carcass is wrapped in a combination of absorbent material with a moisture-vapor-permeable, pliable, extensile film. The meat is wrapped in the film and held under ultraviolet radiation for five, ten, fifteen or twenty days at between 30.degree. F. to 40.degree. F.; for five or ten day periods at 47.degree. F.; for two, three or five days at 60.degree. F.; or for one or two days at 70.degree. F. The covered meat is initially chilled in a cooler at a temperature of about 30.degree. to 45.degree. F. A period of twenty-four to seventy-two hours is required to bring the meat to an initial chill temperature for aging of about 30.degree. F. to 35.degree. F.
U.S. Pat. No. 3,445,240 to Bedrosian et al. discloses tenderizing meat by storage under specific controlled chilled conditions and for definite periods of time in an atmosphere containing controlled amounts of oxygen and carbon dioxide at a high humidity.
U.S. Pat. No. 3,552,297 to Williams relates to an apparatus for aging and flavoring meat at a temperature of around 65.degree. F. to 75.degree. F. The apparatus includes a germicidal lamp and a timer motor for setting the aging process for a period of one to four days. The aging process is conducted in the presence of Thamnidium, an anti-bacteria agent. U.S. Pat. No. 3,663,233 to Keszler teaches a process of tenderizing and cooking meat products by pumping the beef with a liquid tenderizing agent. The beef is heated to a constant temperature and maintained at such temperature to allow tenderizing by the tenderizing agent. The temperature is then raised to cook the meat.
U.S. Pat. No. 3.961,090 to Weiner et al. teaches pumping an aqueous solution into a piece of uncooked beef, vacuum sealing the beef in a bag and cooking the beef "to attain a maximum internal temperature of 131.degree. to 140.degree. F."
U.S. Pat. No. 3,966,980 to McGuckian discloses a method of cooking foods in vacuum packages in a thermostatically controlled hot water bath followed by quick chilling and storage at 28.degree. F. to 32.degree. F. The bath is maintained in a range between 140.degree. F. to 212.degree. F. to cook the meat at least to a "rare" state. The cooked food is thereafter quick chilled for storage. A disclosed advantage of the process is that the meat may be enzymatically tenderized while it is being cooked.
U.S. Pat. No. 4,233,323 to Sway et al. discloses a tenderization process of exposing meat to ultraviolet rays of high intensity.
U.S. Pat. No. 4,346,650 to Zaitsu discloses a bath for sterilizing and cooking food. The process is a two-step process requiring sterilization at about 105.degree. C. (221.degree. F.) to about 140.degree. C. (284.degree. F.). The bath sterilizes and cooks packaged foods.
U.S. Pat. No. 4,983,411 to Tanaka et al. relates to an apparatus used for ultraviolet sterilization and shrink film packaging food. In the packaging step, the food is sprinkled with hot water.
A process of heat treating proteinaceous food product below a cooking temperature by exposure to an elevated temperature is desirable for pasteurizing, aging or both pasteurizing and aging the food product. However, elevated temperatures for periods required to pasteurize food material or to age food material can cause decomposition, i.e., loss of functionality or cooking. Elevated temperatures at shorter periods of time may not accomplish pasteurization or aging or may stimulate bacteria growth causing spoilage.